writeback: check for registered bdi in flusher add and inode dirty

Also a debugging aid. We want to catch dirty inodes being added to
backing devices that don't do writeback.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 5cb32c5b93d8..d3ca0dac1111 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -465,6 +465,12 @@ void static bdi_add_default_flusher_task(struct backing_dev_info *bdi)
         if (!bdi_cap_writeback_dirty(bdi))
                 return;
 
+        if (WARN_ON(!test_bit(BDI_registered, &bdi->state))) {
+                printk(KERN_ERR "bdi %p/%s is not registered!\n",
+                                                        bdi, bdi->name);
+                return;
+        }
+
         /*
          * Check with the helper whether to proceed adding a task. Will only
          * abort if we two or more simultanous calls to
@@ -528,6 +534,7 @@ int bdi_register(struct backing_dev_info *bdi, struct device *parent,
         }
 
         bdi_debug_register(bdi, dev_name(dev));
+        set_bit(BDI_registered, &bdi->state);
 exit:
         return ret;
 }